There have been other discussion threads about specimen-based observations on iNaturalist:
https://forum.inaturalist.org/t/correcting-research-grade-requirements-for-collected-specimens/782
https://forum.inaturalist.org/t/curators-recent-evidence-of-organism-issues/1650
https://forum.inaturalist.org/t/museum-herbarium-collection-digitisation-on-inaturalist-yes-or-no/5374
In previous discussion, there seems to be some consensus that specimens (and not necessarily always one’s own) as observation records are OK as long as the location and date match the original field location and date of the specimen. Marking such observations as captive would only be appropriate if they were captive in their original location.
This does raise the question of what difference there is between an observation based on a museum specimen collected by someone else, versus on a photograph “collected” by someone else. But that would be a question to take up in one of these other threads…